The present invention relates to a water and oil repellent composition which can impart water and oil repellency and an antifouling property to an object.
Heretofore, techniques of coating an object with a hydrophobic solid material having a small surface tension to modify the surface of the object, have been known. For example, there is a technique of treating an object with a low molecular weight hydrocarbon compound, such as a hydrophobic wax, a carbonic acid having at least one long-chain alkyl group in its molecule, an amine or a thiol, an acrylate type or vinyl type high molecular weight compound, or a silicone. However, such a hydrocarbon type low molecular weight compound or a silicone had a disadvantage that it can not impart oil repellency, although it can impart water repellency to an object.
On the other hand, as a technique for imparting water repellency and oil repellency at the same time, it has been common to treat an object with an organic solvent solution or an aqueous dispersion of a polymer containing polymerized units of a polymerizable monomer containing a polyfluoroalkyl group (hereinafter, a polyfluoroalkyl group will be referred to as an Rf group) in its molecule or a copolymer of such a polymerizable monomer with other monomers (hereinafter such polymer and copolymer will be commonly referred to also as an Rf group-containing polymer), or a low molecular weight compound having an Rf group.
The development of such water and oil repellency is caused by formation of xe2x80x9ca surface having a low surface energyxe2x80x9d where the critical surface tension is low, which is formed on the surface of the coating film by a surface orientation of Rf groups. It has been considered that in order to develop both water repellency and oil repellency, the orientation of Rf groups on the surface is important, and, in order to realize the surface orientation of Rf groups, it is necessary that the melting point of fine crystals in the polymer, derived from Rf groups, exists. For this purpose, an Rf group-containing monomer (crystalline Rf group-containing monomer) having a melting point of fine crystals derived from Rf groups, has been used.
This crystalline Rf group-containing monomer achieves the purpose with a view to developing the water and oil repellency, and improvements have been made in other practical functions. For example, an improvement has been made such that in order to improve the durability against e.g. washing, dry cleaning and abrasion, a monomer for providing high hardness or a monomer having a crosslinking reactive group is employed in addition to the crystalline Rf group-containing monomer, or the copolymer obtained is blended with a polymer having high coating film strength.
On the other hand, with respect to a copolymer (crystalline polymer) containing polymerized units of a crystalline Rf group-containing monomer, an investigation has been made to soften the hard hand, or to lower the melting point of Rf groups in order to develop the water repellency under the low temperature curing condition. For example, a case is known wherein a monomer containing a perfluoroalkyl group (hereinafter, a perfluoroalkyl group will be referred to as an RF group) having a wide range of chain length, is copolymerized with an alkyl group-containing monomer. Further, in the same manner, a method is known which uses a silicone containing an RF group having a wide range of chain length.
For example, JP-A-7-173025 (cosmetic composition containing a fluorine type compound and a wax having a specific melting point), JP-A-10-237133 (tetrapolymer comprising RF group (meth)acrylate, stearyl (meth)acrylate and other two types of monomers as essential components), JP-A-10-81873 (mixture of a fluorine type water and oil repellent, and an alcohol having an RF group having a specific chain length or a perfluoropolyether group-containing alcohol) and JP-A-8-109580 (reacted product of an amino group-containing silicone and an Rf group-containing ester compound) may be mentioned as known art.
Meanwhile, as an example of limiting the chain length of an Rf group-containing monomer to be used, JP-A-62-179517 (acryl type heptapolymer wherein the chain length distribution of Rf groups is defined) may, for example, be mentioned, but it contains at least 40% of crystalline Rf group-containing monomers.
Further, there has been a problem that on a surface treated with a water and oil repellent having a crystalline polymer as an active component, the bonding property and the hand are not satisfied at the same time. Namely, even when bonding treatment is attempted to impart various functions on the surface of fiber products treated with a water and oil repellent containing a crystalline polymer, for example, even when it is attempted to bond a film laminate or a seam tape to impart a water proofing property, or even when it is attempted to bond a urethane or acrylic resin to impart moisture permeability and water proofing property, it has been difficult to secure a sufficient bonding property since the crystalline Rf groups impair the bonding property. It has been tried to improve the bonding property by using a copolymer of a crystalline Rf group-containing monomer and a specific monomer such as vinyl chloride. However, this method tends to further harden the hand of fibers, and thus, the bonding property and the hand have not been satisfied at the same time.
In the techniques of this field represented by these known art references, the physical properties are improved from a viewpoint of functions required in addition to the water and oil repellency, without impairing the water repellency and oil repellency attributable to Rf groups. However, since the Rf group-containing crystal polymer is used as the main component, the following demerits resulting therefrom have not been fundamentally overcome.
In conventional water and oil repellents, in order to achieve both of imparting of the water and oil repellency and imparting of the durability, it has been considered essential to use a crystalline Rf group-containing monomer wherein the melting point derived from fine crystals of Rf groups, is high (usually at least 70xc2x0 C.), among crystalline Rf group-containing monomers.
However, if the crystalline Rf group-containing monomer is used, the entire polymer will have high crystallinity derived therefrom, and accordingly, an object coated or treated with such a polymer becomes very hard. For example, in the case of e.g. fiber products which should naturally be flexible, their flexible hand may be impaired, or since the coating film is hard and brittle, a defect such as a hand mark or a chalk mark formed during handling of the object, tends to remain on the whole cloth as the final product.
Further, there has been a demerit that a high water and oil repellency may be developed in the initial stage after the treatment, such performance tends to be extremely deteriorated by abrasion during the usage or by repeated washing. Namely, a water and oil repellent which can maintain the initial performance stably, has been desired. Further, on the coating film, shortage in the bonding property of the surface, or cracks or fractures which deteriorate the quality of the object tend to result, and therefore, it has been desired to overcome such problems so that this type of water and oil repellent can be applied to a wider range of materials.
Further, when a crystalline polymer is used as the main component, in order to obtain a uniform coating film having high water and oil repellency, usually, a process has been essential wherein after the coating, a high temperature treatment at a temperature higher than the melting point of fine crystals, is applied to melt the polymer, followed by cooling to form the film. However, if such a high temperature treatment is applied, there has been a case where a problem such as deterioration of color fastness, hardening of the hand or a fading, is induced and the quality of treated objects is further deteriorated, in the case of fiber products made of materials such as extrafine-denier fibers or modified cross-section fiber.
Heretofore, in order to solve the problems of crystalline polymers, such a technique as lowering the crystallinity of the polymers, or making the polymers flexible, is known. Further, for the purpose of forming a film at a low temperature, such a technique as using a film-forming auxiliary agent, or copolymerizing a polymerizable monomer containing a branched alkyl group having an internal practicizing effect, with a crystalline Rf group-containing monomer, is known. However, in such a case, since the crystals derived from Rf groups to develop water and oil repellency, are partially destroyed, there has been a problem such as developing no adequate water and oil repellency, or deterioration of the durability.
The present inventors have made detailed studies with respect to a totally new mechanism for developing water and oil repellency. And it has been astonishingly found that by combining an Rf group-containing monomer which has not been used in the field of water repellent coating since the melting point attributable to the fine crystals of Rf groups in its homopolymer does not exist or is low, with a crystalline hydrocarbon type monomer whose homopolymer does not develop water and oil repellency, the crystallinity attributable to the crystalline hydrocarbon type monomer can be strengthened. Namely, it has been found that by a synergistic effect of strengthening the surface orientation, the water and oil repellency can be developed even if fine crystals derived from Rf groups in the polymer do not exist, or even if the melting point of such fine crystals is low.
In the water and oil repellent based on this principle, fine crystals derived from Rf groups in the polymer do not exist or the melting point thereof is not high. Accordingly, the water and oil repellency can be imparted to objects without accompanying deterioration of the quality due to e.g. hardening of the hand or embrittlement of the coating film, which has been a conventional problem. Further, sufficient water and oil repellency can be imparted even if a treated object is treated at a temperature lower than before. Further, the deterioration of the performance is less even by e.g. abrasion or washing.
The present invention provides a water and oil repellent composition essentially containing a copolymer consisting essentially of polymerized units of the following monomer (a) and polymerized units of the following monomer (b):
monomer (a): a monomer having an Rf group, wherein the melting point of fine crystals derived from the Rf groups in a homopolymer of said monomer, does not exist or is at most 50xc2x0 C.,
monomer (b): a monomer having an organic group other than an Rf group, wherein the melting point of fine crystals derived from the organic groups in a homopolymer of said monomer, is at least 30xc2x0 C.
In the present invention, it is important to contain polymerized units of monomer (a) (hereinafter, it may be referred to as an Rf monomer) wherein the melting point of fine crystals derived from Rf groups of the homopolymer does not exist or is at most 50xc2x0 C. Further, in the present invention, it is also important to contain polymerized units of monomer (b) having an organic group other than an Rf group, which is copolymerizable with the Rf monomer, and wherein the melting point of fine crystals derived from the organic groups in its homopolymer, is at least 30xc2x0 C. The copolymer of the Rf monomer and monomer (b) is substantially essential in the present invention.
Monomer (a) used in the present invention, may be a mixture of at least two types of Rf monomers.
The presence or absence of the melting point of fine crystals derived from Rf groups, can be confirmed by a differential calorimetry (a DSC measurement method described in JIS-K-7121-1987 and K-7122-1987). In the case of this method, when the calorie accompanying to the melting or solidification of the fine crystals is at most 3 kJ/mol, it is judged that the Rf group-containing polymer do not contain fine crystals.
The presence or absence of fine crystals derived from Rf groups can be confirmed also by observing a peak attributable to their self packing by means of a wide angle or small angle X-ray scattering. If the fine crystals are present in the polymer, usually the spacing of their characteristic packing planes is observed to be about 5 xc3x85.
The Rf monomer means a compound having an R group and a polymerizable unsaturated group. The Rf monomer is preferably a compound represented by the formula (Z-Y)nX wherein an Rf group Z and a polymerizable unsaturated group X are bonded to each other via a specific bivalent organic group Y. Here, Z is an RF group having a number of carbon atoms of at most 6, or a group represented by the formula CmF2m+1O(CF2CF(CF3)O)dCF(CF3)xe2x80x94 (m is an integer of from 1 to 6, and d is an integer of from 1 to 4), n is 1 or 2, and when n is 2, two (Z-Y) may be the same or different from each other. X may be xe2x80x94CRxe2x95x90CH2, xe2x80x94COOCRxe2x95x90CH2, xe2x80x94OCOCRxe2x95x90CH2, xe2x80x94OCH2xe2x80x94xcfx86xe2x80x94CRxe2x95x90CH2 or xe2x80x94OCHxe2x95x90CH2 when n is 1, and may be xe2x95x90CH(CH2)qCRxe2x95x90CH2, xe2x95x90CH(CH2)qCOOCRxe2x95x90CH2, xe2x95x90CH(CH2)qOCOCRxe2x95x90CH2 or xe2x80x94OCOCHxe2x95x90CHCOOxe2x80x94 (R is a hydrogen atom, a methyl group or a halogen atom, xcfx86 is a phenylene group, and q is an integer from 0 to 4) when n is 2. Further, Y is a bivalent organic group or a single bond.
The Rf group is a group having a part or all of hydrogen atoms of an alkyl group substituted by fluorine atoms, and its carbon number is preferably from 1 to 20. The Rf group is preferably a group having at least from 20 to 80% in number of hydrogen atoms of an alkyl group substituted by fluorine atoms. Further, a part or all of the remaining hydrogen atoms may be substituted by chlorine atoms. The Rf group may be of linear type or branched type. In the case of branched type, one having a short branch at the end far from the connecting bond or in the vicinity of the end, is preferred.
Among the above-mentioned preferred Rf groups, a linear RF group represented by the formula F(CF2)kxe2x80x94 (k is an integer of from 1 to 20), or a group represented by the formula CjF2j+1(CM1M2CM3M4)ixe2x80x94 (M1, M2, M3 and M4 are each independently a hydrogen atom, a fluorine atom or a chlorine atom, and one of them is a fluorine atom, and j and i are each an integer of at least 1 and satisfy 20xe2x89xa7(j+2xc3x97i)xe2x89xa76), is preferred. Particularly, an RF group having a carbon number of at most 6, or a group represented by the formula CmF2m+1O(CF2CF(CF3)O)dCF(CF3)xe2x80x94 (m is an integer of from 1 to 6, and d is an integer of from 1 to 4), is preferred.
The carbon number of the Rf group is preferably from 1 to 20, particularly preferably from 1 to 12. One having a small carbon number is preferred since fine crystals derived from the Rf groups are not likely to be formed when the homopolymer is formed, and the copolymer can form a flexible film. The Rf group may be a linear polyfluorohydrocarbon group having at least one unsaturated group such as carbonxe2x80x94carbon unsaturated double bond.
The Rf group may be a polyfluorooxaalkyl group having a part of its carbon atoms substituted by etheric oxygen atoms. Particularly, a polyfluorooxaalkyl group (particularly, a perfluorooxaalkyl group) having at least one perfluorooxypropylene group, is preferred. The carbon number in this case is preferably from 6 to 18 including carbon atoms before substituted by oxygen atoms.
A specific Rf group may be one of the following Rf groups, but is not limited thereto:
F(CF2)4xe2x80x94, F(CF2)5xe2x80x94, F(CF2)6xe2x80x94, (CF3)2CF(CF2)2xe2x80x94, H(CF2)6xe2x80x94, HCF2CF2xe2x80x94, Cl(CF2)4xe2x80x94, F(CF2)4(CH2CF2)3xe2x80x94, F(CF2)6(CH2CF2)3xe2x80x94, F(CF2)4(CFClCF2)2xe2x80x94, CF3CFxe2x95x90CFCF2CFxe2x95x90CFxe2x80x94, CF3CF2C(CF3)xe2x80x94CH(CF3)(CF2CF3), CeF2e+1O[CF(CF3)CF2O]hxe2x80x94CF(CF3)xe2x80x94 or C3F7O[CF(CF3)CF2O]h(CF2)vxe2x80x94 (e is an integer of from 3 to 6, h is an integer of from 0 to 3, and v is an integer of from 2 to 6).
The Rf group and the polymerizable unsaturated group may be bonded by a single bond or via a bivalent organic group. As the bivalent organic group, a group containing an alkylene group is preferred. The alkylene group may be linear or one having a branch. Further, in the bivalent organic group, e.g. xe2x80x94Oxe2x80x94, xe2x80x94NHxe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94SO2xe2x80x94 or xe2x80x94CD1=CD2xe2x80x94 (D1 and D2 each independently represents a hydrogen atom or a methyl group) may be contained. As the bivalent organic group, an alkylene group is preferred.
As Y, a bivalent organic group represented by the formula xe2x80x94RM-Qxe2x80x94RNxe2x80x94 (RM and RN each independently represents a single bond or a saturated or unsaturated hydrocarbon group having a carbon number of from 1 to 22 which may contain at least one oxygen atom, and Q represents a single bond, xe2x80x94OCONHxe2x80x94, xe2x80x94CONHxe2x80x94, xe2x80x94SO2NHxe2x80x94 or xe2x80x94NHCONHxe2x80x94) is preferred.
As Y, xe2x80x94CH2xe2x80x94, xe2x80x94CH2CH2xe2x80x94, xe2x80x94(CH2)11xe2x80x94, xe2x80x94CH2CH2CH(CH3)xe2x80x94, xe2x80x94CHxe2x95x90CHCH2xe2x80x94, xe2x80x94(CH2CHR2O)wCH2CH2xe2x80x94 (w is an integer of from 1 to 10, and R2 represents a hydrogen atom or a methyl group), xe2x80x94C2H4OCONHC2H4xe2x80x94, xe2x80x94C2H4OCOOC2H4xe2x80x94 or xe2x80x94COOC2H4xe2x80x94 may, for example, be preferably mentioned.
As X, an ethylenic polymerizable unsaturated group, namely, e.g. a residue of an olefin, a residue of a vinyl ether, a residue of a vinyl ester, a residue of a (meth)acrylate, a residue of a maleic acid ester or a residue of a fumaric acid ester, is preferred. Here, the residue of an olefin means a group represented by xe2x80x94CRxe2x95x90CH2, the residue of a vinyl ester means a group represented by xe2x80x94COOCRxe2x95x90CH2, the residue of a vinyl ether means a group represented by xe2x80x94OCRxe2x95x90CH2, the residue of a (meth)acrylate means a group represented by xe2x80x94OCOCRxe2x95x90CH2, and the residue of a maleic acid or fumaric acid ester means a group represented by xe2x80x94OCOCHxe2x95x90CHCOOxe2x80x94. In addition to these, xe2x80x94OCH2-xcfx86-CRxe2x95x90CH2 and xe2x80x94OCHxe2x95x90CH2 may, for example, be mentioned (xcfx86 represents a phenylene group).
Here, R is preferably a hydrogen atom, a halogen atom (a fluorine atom, a chlorine atom, etc.) or a short-chain alkyl group having a carbon number of from 1 to 3 (particularly a methyl group), in order not to hinder polymerization. In consideration of the polymerizability to form a copolymer, X is preferably a residue of a (meth)acrylate, or a residue of maleic acid or fumaric acid ester, and from the viewpoint of e.g. the solubility in the solvent or easiness of emulsion polymerization, the residue of a (meth)acrylate is particularly preferred.
As the Rf monomer, particularly a (meth)acrylate having an Rf group is preferred. As such an Rf monomer, various monomers such as the following monomer (a) may be used. As such monomers, known monomers may be used. As the monomer (a) employed in the present invention, a (meth)acrylate is particularly preferred as mentioned above from the viewpoint of e.g. the polymerizability with other monomers, flexibility of the film to be formed, adhesion to the substrate, solubility in the solvent and easiness of emulsion polymerization.
In a case of a (meth)acrylate where the Rf group is an RF group, and Y is xe2x80x94(CH2)xe2x80x94, xe2x80x94(CH2CH2)xe2x80x94 or xe2x80x94(CH2)3xe2x80x94, if the carbon number is at least 7, the melting point of fine crystals will be present and the objective function will not be developed, and such a monomer is excluded from the monomer (a) to be employed in the present invention. In such a case, the Rf group is preferably an RF group having a carbon number of at most 6. And, it is most preferably a linear RF group having a carbon number of from 4 to 6.
When Y is xe2x80x94CH2CH2CH(CH3)xe2x80x94 or xe2x80x94CHxe2x95x90CHxe2x80x94CH2xe2x80x94 and X is a (meth)acrylate, the carbon number of the Rf group is preferably from 1 to 10, particularly preferably from 4 to 8. When the Rf group is a polyfluoropolyether group containing an oxygen, and X is a (meth)acrylate, the carbon number of the Rf group is preferably from 4 to 18.
As the monomer (b) of the present invention, a (meth)acrylate, a vinyl ether or a vinyl ester may preferably be mentioned. The monomer (b) may contain a small number of isolated fluorine atoms which are usually not regarded as Rf groups. Further, as an organic group contained in the monomer (b), a long-chain hydrocarbon group wherein the melting point of fine crystals is at least 30xc2x0 C., is preferred.
As the monomer (b) having a long-chain hydrocarbon group, a monomer having a linear hydrocarbon group having a carbon number of at least 14, particularly a monomer having a linear saturated alkyl group having a carbon number of from 16 to 24, is preferred. As the monomer (b), a (meth)acrylate containing a saturated hydrocarbon group having a carbon number of at least 15, is particularly preferred. Further, a vinyl ester containing a saturated hydrocarbon group having a carbon number of at least 15, is also preferred.
The molar ratio of polymerized units of monomer (a)/polymerized units of monomer (b) in the copolymer is preferably from 0.1/1 to 9/1, more preferably from 0.2/1 to 5/1, particularly preferably from 0.2/1 to 1.5/1. The composition in this range is excellent in the water and oil repellency and in the flexibility of the film, such being preferred. Further, the copolymer may contain a monomer (also referred to as another monomer) other than the monomer (a) and the monomer (b), for the purpose of improving physical properties other than the water and oil repellency, such as the adhesion to a substrate, the bonding property, and the durability against abrasion.
Another monomer may, for example, be ethylene, vinylidene chloride, vinyl chloride, vinylidene fluoride, vinyl acetate, styrene, xcex1-methylstyrene, p-methylstyrene, glycidyl (meth)acrylate, (meth)acrylamide, N,N-dimethy(meth)acrylamide, diacetone(meth)acrylamide, methyloldiacetone(meth)acrylamide, N-methylol(meth)acrylamide, vinyl alkyl ether, an alkyl vinyl ether halide, a vinyl alkyl ketone, butadiene, isopropylene, chloroprene, aziridinylethyl (meth)acrylate, benzyl (meth)acrylate, aziridinyl (meth)acrylate, a polyoxyalkylene (meth)acrylate, a methylpolyoxyalkylene (meth)acrylate, a 2-ethylhexylplyoxyalkylene (meth)acrylate, a polyoxyalkylene di(meth)acrylate, a (meth)acrylate having polysiloxane, triallyl cyanurate, allylglycidyl ether, allyl acetate, N-vinylcarbazole, maleimide, N-methylmaleimide, (2-dimethylamino)ethyl (meth)acrylate, a (meth)acrylate having an alkyl group having a carbon number of from 8 to 20, a cycloalkyl (meth)acrylate, hydroxyethyl (meth)acrylate, glycerol (meth)acrylate, a (meth)acrylate having a silicone in its side chain, a (meth)acrylate having an urethane bond, an alkylenedi(meth)acrylate or polyoxyalkylene di(meth)acrylate.
Particularly, vinyl chloride, a hydroxyethyl (meth)acrylate having a reactive group such as a hydroxyl group in its molecule, a polyoxyalkylene (meth)acrylate, a methylpolyoxyalkylene (meth)acrylate, a glycidyl (meth)acrylate, a bifunctional polyoxyethylene di(meth)acrylate, ethyleneglycoldi(meth)acrylate or a blocked isocyanate ethyl (meth)acrylate, is preferred with a view to improving the adhesion to a substrate, of the composition including the copolymer.
In the water and oil repellent composition of the present invention, the method of preparing the copolymer to be the active component, is not particularly limited. For example, a common polymerization method such as a solution polymerization method using an organic solvent, a dispersion polymerization method using water as a dispersion medium and containing a nonionic surfactant and/or a cationic surfactant, or an emulsion polymerization method, may be employed. The obtained solution, dispersion or emulsion of the copolymer may be used as it is, or may be used as diluted. Otherwise, the copolymer may be isolated, and then, dissolved, dispersed or emulsified in a solvent, dispersion medium or emulsion medium.
The form of the water and oil repellent composition is preferably an aqueous dispersion containing a small amount of a surfactant and/or an organic solvent considering the easiness in handling. Further, various additives such as a penetrant, a defoaming agent, a water absorbent, an antistatic agent, an anticrease agent, a hand adjusting agent, a film-forming auxiliary agent, a water soluble polymer such as polyacrylamide or polyvinyl alcohol, a melamine resin or a urethane resin, may be incorporated to the composition, as the case requires.
The water and oil repellent composition of the present invention is useful for a water and oil repellent treatment of e.g. working cloths or uniforms. Further, it is also useful for an application as a coating agent for filtration materials to be used in the presence of an organic solvent liquid or its vapor, as a surface protecting agent, as a coating agent for electronics or as an antifouling coating agent.
When an object is treated with the water and oil repellent composition of the present invention, if the object is a fiber product, the hand becomes flexible since the coating film is flexible, and high quality water and oil repellency can be imparted to the object. Further, since the fine crystals derived from Rf groups are not contained, the composition is excellent in the bonding property of the surface, and can impart water and oil repellency even by curing at a low temperature. Further, the deterioration in performance by abrasion or by washing is less, and accordingly the performance of initial treatment can be maintained stably. Further, when paper is treated with the composition, an excellent sizing property, water repellency and oil repellency can be imparted to the paper even under low temperature short drying conditions.
There is no particular restriction as to the object to be treated with the water and oil repellent composition of the present invention, and it may, for example, be a fiber product made of e.g. a natural fiber, a synthetic fiber or a blended fiber thereof, a metal, a glass, a resin, a paper or a leather.